1. Field of the Invention
This invention relates to a lubricating oil pump for use in an internal combustion engine which can feed a varying quantity of lubricating oil in response to the engine load.
2. Description of the Prior Art
The quantity of lubricating oil required by an internal combustion engine generally varies in proportion to the engine speed and engine load. A too small quantity of lubricating oil will cause an engine seizure; while an excessive quantity of lubricating oil will result in various disadvantages, such as waste of oil, air pollution and failure of smooth engine operation due to deposition of carbon and excessive oil onto the sparking plug and walls of the combustion chamber.
A conventional lubricating oil pump for use in an internal combustion engine is provided with a plunger which is forced to reciprocate by means of a cylindrical cam member. The plunger has a stroke which varies depending on the throttle angle, so that a sufficient quantity of lubricating oil can be supplied even under such conditions where the throttle valve is full-opened.
It is desirable to vary the supply quantity of lubricating oil in response to depending on the engine load. In the conventional lubricating oil pump, however, the plunger stroke is predetermined on the one hand by the cylindrical cam member. This means that to increase the plunger stroke the cylindrical cam member must be made large in size. In contrast, in a conventional lubricating oil pump, the plunger stroke varies according to the throttle angle. The throttle angle, however, remains constant unless it is varied positively. Furthermore, since the plunger stroke cannot be varied in response to the engine speed, the quantity of lubricating oil fed out of the conventional lubricating oil pump remains constant even when a variation is encountered in the engine speed. The variation in the engine speed results in the variation in the output torque and, hence, the constant supply of lubricating oil is turned out to be either excessive or insufficient. An optimum oil supply cannot be attained especially when the engine under idling or low-load operation is accelerated rapidly.